A system for simultaneously proving coolant at one temperature to the cylinder jackets of a diesel engine and coolant at a low temperature to the engine air-charge intercooler, with the use of a single pump, heat exchanger, and temperature control valve. Only that portion of the coolant going to the...http://www.google.com/patents/US3863612?utm_source=gb-gplus-sharePatent US3863612 - Cooling system

A system for simultaneously proving coolant at one temperature to the cylinder jackets of a diesel engine and coolant at a low temperature to the engine air-charge intercooler, with the use of a single pump, heat exchanger, and temperature control valve. Only that portion of the coolant going to the intercooler passes through the heat exchanger, with the discharge thereof mixing with the engine coolant discharge to bring its temperature down to the desired engine coolant temperature. The temperature control valve controls the amount of coolant going through the heat exchanger so that the engine coolant remains at substantially the desired temperature.

It is known in the art to control the temperature in a cooling system by the use of a temperature sensitive valve to regulate the coolant flow in a system having a heat exchanger and circulating pump. Selective placement of the valve determines the point in the system where a constant temperature is to be maintained. Such a system is conventionally used in automotive applications wherein a three-way thermostatic valve regulates the engine water temperature by modulating the flow of coolant discharge passing through either a radiator or a by-pass line to the pump. This system is used for maintaining a desirable coolant temperature and flow relationship to effectively cool a single heat element.

In some instances, it is desirable to cool more than one element in a system, with the heated elements having different coolant temperature requirements. For example, in a diesel engine apparatus, where the air charge is compressed by a turbocharger, it is desirable to cool the compressed air as well as the engine itself. However, to maintain turbine inlet temperature within a tolerable limit, it may be necessary to maintain the coolant into the intercooler which cools the engine air at a considerably lower level than that of the coolant for the cylinder jackets. Ordinarily, this requires two separate cooling systems complete with pumps, heat exchangers and temperature control valves, thereby amounting to considerable expense in installation and maintenance.

It is therefore an object of this invention to provide a cooling system for cooling plural heat sources having substantially different temperature requirements.

Another object of this invention is the provision in a cooling system for diverse coolant temperatures with a singular thermostatic valve and heat exchanger.

Yet another object of this invention is the provision in a cooling system for maintaining a substantially constant coolant temperature into one element of the system while providing coolant at a considerably lower temperature to another element in the system.

Still another object of this invention is the provision for an engine cooling system which is economical to manufacture and operate.

These objects and other features and advantages become more readily apparent upon reference'to the following description when taken in conjunction with the appended drawings.

SUMMARY OF THE INVENTION Briefly, in accordance with one aspect of the invention, a closed cycle cooling system simultaneously provides liquid coolant at different temperatures to each of two connected machines or machine elements to be cooled using a single pump, temperature control valve and external heat exchanger. The flow of coolant to each of the cooled machines is in a constant preset proportion with the temperature of the flow to one being regulated while the temperature to the other decreases as the load is increased. All the external cooling is done on the coolant that flows through the machine or element requiring the lower temperature. After passing through and cooling that machine, its temperature is still lower than that of the coolant leaving the other machine. Mixing of the two coolant streams results in coolant at the regulated temperature being supplied to the regulated temperature machine and to the temperature control valve.

The underlying principle is that of removing the entire heat load from only a fraction of the coolant flow, thereby reducing its temperature substantially below that which result by taking the same amount of heat out of the total coolant flow. The same principle may be applied in an unregulated temperature system, without a temperature control valve, to provide colder coolant to one of two cooled elements.

The closed coolant circuit consists of a pump, a first machine element requiring cooling, a second machine element requiring cooling to a lower temperature, a heat exchanger, and interconnecting piping or passages.

The flow out of the pump divides in two branches,

one going to the first machine to be cooled, the other going to the heat exchanger, thence to the machine to be cooled to a lower temperature. Leaving the cooled machines, the flow branches join and the coolant returns to the pump inlet for recirculation.

For a regulated temperature system, a temperature sensor and a temperature control valve are provided and may be located either in the closed coolant circuit or external to it, depending on the: particular effect and arrangement desired.

When used in a diesel engine cooling system, a proportionate amount of total coolant flow is passed through the engine at a desired temperature. The other portion is directed to a temperature sensitive valve which modulates, in response to the coolant temperature, the coolant flow to the intercooler between two flow paths, one through a heat exchanger and the other through a by-pass. The heat exchanger then receives only a small portion of the entire coolant flow and cools it to a greater degree than is done in a conventional system. The coolant discharge from the heat exchanger passes to the intercooler along with the by-pass flow, and the resultant mixture is formed at a considerably ,lower temperature than the coolant to the engine,

thereby allowing for increased cooling of the compressed air and greater power output in engine operatlon.

Discharge coolant from the intercooler mixes with the engine coolant discharge, and the total coolant flow is pumped back toward the engine. The pump speed determines the rate at which the total coolant flows. However, there is a constant proportionate coolant flow in both the engine and the intercooler, the coolant into the engine being held at a regulated temperature, and the coolant into the intercooler being at a temperature lower than that into the engine, the temperature difference increasing with engine load.

In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a schematic view of the preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the invention is shown generally at and will be described in terms of usage with an internal combustion engine 11 having a compressor, 15, for compressing the combustion air to the engine 11, with the compressed air charge being cooled by an intercooler 12. A typical system of this type is that of a diesel engine, wherein a turbocharger is driven by the exhaust gases from the engine, and the resultant power is utilized to compress the ambient air before it is directed to the cylinders. Since it is desirable to cool the compressed air and to reduce the maximum combustion temperature and the turbine inlet temperature, the intercooler has become a standard element in such diesel engine systems.

The primary heat source which requires cooling is the engine cylinders, and this cooling function is accomplished by passing a coolant, such as water or the like, to an engine inlet line 13, through the engine cylinder jackets 11, and out an engine discharge line 14. It is desirable to maintain the temperature of the coolant into the engine inlet line 13 at a substantially constant value and to maintain a substantial flow of coolant through the engine during all periods of operation. Coolant flow to the engine is maintained by a standard pump 16, typically one of the centrifugal type, having an inlet line 17 and discharge line 18. The pump is generally driven by the engine, and therefore the rate of total coolant flow therethrough is determined by the operating speed of the engine 11.

Connected to and fluidly communicating with the pump discharge line 18 is a valve inlet line 19 for proportioning the total coolant flow between lines 13 and 19. The system is hydraulically balanced, as for example, by design or by fixed orifices, so that the flow rates to the engine inlet line 13 and the valve inlet line 19 are in the desired ratio. The inlet line 19 leads to a temperature controlled three-way valve 21 having ports B, C and E. The control valve is of the standard commercially available type, having an integral sensor to sense the temperature of the coolant coming to the E port and modulating the flow to the C and B ports to maintain the temperature at E and at the engine inlet at the desired value. It modulates, in response to the temperature of the coolant in line 19, the proportional flow of coolant to a by-pass line 22 and to a heat exchanger inlet 23. That portion of the coolant going to the line 23 passes through a heat exchanger 24 where it is cooled by the external cooling medium such as air or water or the like, then flows out the discharge line 25, where it mixes with the coolant from the by-pass line 22 to cool it. The combined flow then goes through the inlet line 26 to the intercooler 12 where it takes heat from the compressed combustion air. With the engine operating under load, the temperature of the coolant in line 26 is substantially below that of the coolant in line 13, thereby providing a very substantial cooling effect to the compressed air. The temperature difference between the engine coolant and the intercooler coolant is determined by the engine load. As will be seen by the examples presented hereinafter, when operating under full load conditions this temperature difference will be at a maximum and result in maximum cooling of the combustion air, whereas when operating at reduced loads, the temperature difference and the amount of heat taken from the charge air by the intercooler will accordingly be reduced.

Coolant from the intercooler passes through the outlet line 27 to the main line 28 where it mixes with the coolant discharge from the engine to cool it. The total coolant flow then passes to the pump through inlet line 17. It should be noted that another heat source, such as an oil cooler, may be placed in line 28, and in such case the temperature of the coolant mixture would be brought to a temperature below that of the coolant into the engine, such that after leaving the oil cooler it would be of the desired temperature. An expansion tank 29 may be provided to accommodate variations in coolant and ambient temperatures and pressures. It should be noted that the integral sensor may just as well be replaced by a remote sensor installed in the engine inlet line 13, with the temperature control valve 21 being equipped for remote sensing. Alternatively, if it is desirable to control the temperature of the engine coolant discharge, it may be regulated by connecting the remote sensor in the discharge line 14.

It would not be particularly desirable in a diesel engine installation to regulate the temperature of the coolant to the intercooler and allow the coolant to the engine to float at a higher temperature. However, there may be various other cooling schemes wherein the engine and intercooler of FIG. 1 are replaced by elements having different temperature requirements and the coolant to the element requiring the cooler temperatures is preferably regulated and that to the element requiring the warmer temperatures can be allowed to float. These requirements can be met by the identical placement of the control valve as described above but with the remote sensor placed in either of the inlet or outlet lines, 26 or 27. Also, the remote sensor may be placed in the line 31 to regulate the charge air temperature.

Another valve and sensor arrangement which may be used is that shown in FIG. 2 which will be described hereinafter.

In a typical opereational example of the diesel engine installation shown in FIG. 1, the engine is started and the coolant circulates through the system. It is desirable to maintain the temperature of the coolant into the engine at a temperature of and that into the intercooler at a lower temperature. Until the coolant temperature approaches 175, the thermostatically con trolled valve 21 passes all of the coolant from line 19 directly to the intercooler 12, by-passing the heat exchanger and facilitating warm-up of the coolant to the engine. Upon the coolants reaching the desired temperature, the valve 21 then acts to pass portions of the coolant to the heat exchanger, thereby preventing the temperature from increasing beyond 175. As the load on the engine is increased, a greater amount of cooling is required to maintain the desired temperature. Accordingly, more coolant is routed through the heat exchanger, thereby resulting in lower temperatures at the intercooler and greater cooling effect on the compressed air. Since operation of the engine at a higher load condition causes the turbocharger to operate at a higher compressor pressure ratio thereby increasing the temperature of the compressor discharge air entering the intercooler, this is a highly desirable relationship.

Assume that the system is operating under a full load condition and the temperature rises at the engine and intercooler are F and F, respectively. Assume also that the total coolant flow is 100 gallons per minute of which 75 gpm flows through the engine and gpm through the intercooler. Assuming further that the coolant is water, the heat rejections for the engine and intercooler are then as follows:

Since the heat rejection must all be taken out of the 25 gpm flowing to the intercooler, the temperature drop across that portion is then A T 625,000/(25 X 60 X 8.33) 50F Thus the temperature of coolant into the intercooler is 175 50 125F, and the temperature out is l45F.

At the engine, the coolant enters at 175 and leaves at 185F. When combined with the coolant discharge from the intercooler, the mixture temperature can be expressed by the following formula:

75(T AT 25(T AT2)/100 T where T coolant temperature into pump AT coolant temperature change through engine T coolant temperature into intercooler AT coolant temperature change through intercooler This indicates that the temperature of the coolant mixture from the engine and intercooler outlets equals the temperature of the water into the pump. In the example given:

If the load on the engine and/or compressor is decreased with the coolant flow remaining constant, the temperature rises across the engine and/or compressor will decrease resulting in a lower temperature of coolant into the pump. This will be sensed by the thermostatically controlled valve which will divert more of the coolant directly to the intercooler by-passing the heat exchanger and raising the temperature of the coolant to the intercooler to restore the temperature of the merged coolant to the desired value.

For example, if the load on the engine and compressor were each reduced so that the heat rejection was only 20 percent of the original value, then the total heat rejection would be 0.2(625,000) 125,000 BTU/hr The temperature drop of the coolant flowing to the in tercooler is AT=125,000/(25 X 60 X 8.33) 10F The temperature rise across the engine is AT, 0.2(10) 2F. The temperature rise across the intercooler is AT 0.2(20) 4F. The following coolant temperatures then exist:

Engine temperature in 175F Engine temperature out 177F lntercooler temperature in F lntercooler temperature out l6 9F and the coolant temperature after merging is again It can therefore be seen that after an initial warming up period the temperature of the coolant to the pump and engine remains constant. Also, the temperature of the coolant to the intercooler is lower than that constant temperature by an amount determined by the amount of combined heat rejection of the engine and compressor. Greater loads cause greater differences in the respective coolant temperatures. As a no-load condition is approached the temperatures to the engine and intercooler become equal at F.

This indirect relationship between the engine load or magnitude of the heat source and the temperature of the coolant to the intercooler, facilitates combustion in cold weather by warming the intake air when the engine is idling or lightly loaded Typically an intercooler or a "turbocharged engine operating at full load with cooling water in at 170F and air in from the compressor at 370F will cool the air to the engine to about F.

On a cold day with the engine idling the same intercooler will bring the air temperature to within l0-l5 ofthe temperature of the water entering the'intercooler orabout l55F. Assuming the ambient air temperature is 0F and the engine has volumetric compression ratio of 12, the temperature at the end of the compression stroke will be about ll20F versus about 800F if the air was not heated by the intercooler. The higher temperature facilitates compression ignition and combustion of the fuel during periods in which the engine is operating in an idle condition. In certain applications, as for example in railway locomotive engines, it is common practice to idle the engine during approximately 40 percent of the operating time. In cold weather the warming effect of the intercooler on the combustion air charge is important.

Generally the same locomotive is operating under full power during much of the remaining 60 percent of use time. As mentioned hereinbefore, during these periods critical operating temperatures are reduced by having a maximum manifold air cooling capacity. This is automatically achieved by decreasing the intercooler coolant temperature as the load increases.

Tests of internal combustion engines have shown that reduced inlet air temperatures bring about a major reduction in exhaust emissions of nitrides of oxygen (NO For example, at full power they can be reduced to as low as 20 percent of those produced when operating with normal inlet air temperatures.

Other advantages offered by the provision of lower air temperature include reductions in engine combustion temperature, turbine operating temperatures and exhaust temperature for the same power output, thereby improving parts life and reducing the requirements for temperature derating. In many engines the lower temperatures will permit increased power output.

Another advantage is the fact that all of the cooling is done on a fraction of the flow thereby permitting smaller-piping and flexibility in the design of the external heat transfer system. Further, the present system provides full coolant flow to the machines at all times,

Other applications of the present system include but are not limited to engine driven compressors where improved compression efficiency and reduced fuel consumption can be achieved by supplying colder water for compressor intercooling, and liquid cooled gas turbines where colder temperatures are desired for compressor intercooling than for turbine cooling.

Referring now to FIG. 2, the apparatus is substantially the same as that shown in FIG. 1 except that the by-pass line and temperature control valve are removed. This arrangement shows the basic concept contemplated by the invention, i.e., to provide colder coolant to one of two cooled elements by removing the entire heat load from that portion of total coolant flowing to the colder element. This may be accomplished without the temperature control valve if there is no necessity to regulate one of the temperatures as described hereinabove.

If it is desired to regulate a temperature somewhere in the system and it is desired not to modulate the coolant flow in the system a temperature controlled device 32 can be used to control the amount of cooling by modulating the flow of the external cooling medium through the heat exchanger or radiator. If the external cooling medium is liquid, the temperature controlled device is preferably a two way temperature controlled valve. If a radiator is used and the external cooling medium is air or gas, then controllable louvres are used to modulate the flow. Coolant temperatures are sensed by a sensor 33 in much the same manner as that described for the apparatus of FIG. 1. Again, the regulated ternperature point may be that in line.19 or it may be 10- cated at any one of the points described above by the use of a remote sensor.

It should be noted that the temperature controlled device 32 may just as well modulate the flow of the external cooling medium by being placed at a point downstream of the heat exchanger.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A cooling system comprising:

a. a first heat source to be cooled by the flow therethrough of a coolant at a first temperature;

b. a second heat source to be cooled by the flow therethrough of a coolant at a second temperature lower than said first temperature;

c. means for combining the total discharge flows from said first and second heat sources to form a coolant mixture at a temperature no higher than that of said first temperature;

d. means for pumping said coolant mixture toward the inlets of said first and second heat sources;

e. means for proportioning the total coolant mixture flow between said first and second heat sources; and

f. a heat exchanger means for cooling that proportion of coolant being delivered to the inlet of said second heat source.

2. A cooling system as set forth in claim 1 and including a by-pass line installed around said heat exchanger, such that a portion of the coolant flowing to said second heat source does not pass through said heat exchanger but instead passes to said second heat source by way of the by-pass line.

3. A cooling system as set forth in claim 2 and including a temperature controlled valve fluidly interconnecting said proportioning means to said heat exchanger and said by-pass line, for proportioning the amount of coolant flow to each in response to an existing temperature condition in the system.

4. A cooling system as set forth in claim 3 and including a sensor for sensing the temperature of said coolant mixture and modulating said temperature controlled valve in response thereto to cause the temperature of said mixture to be maintained at substantially a constant desired level.

5. A cooling system as set forth in claim 4 wherein said sensor forms an integral part of said temperature controlled valve.

6. A cooling system as set forth in claim 1 wherein said heat exchanger has an external cooling medium flowing therethrough and further wherein means is provided to modulate the flow of the external cooling medium through said heat exchanger.

7. A cooling system as set forth in claim 6 and further including a temperature sensitive device for operating said modulation means in response to an existing temperature condition in the system.

8. A cooling system as set forth in claim 7 and including a sensor for sensing the temperature of said coolant mixture and further wherein said modulation means tends to operate so as to maintain the temperature of said coolant mixture at a substantially constant desired level.